Counting Unit Cubes
Measure volumes by counting unit cubes using cubic cm, cubic in, cubic ft, and other units
What a learner can do afterwards
- Count unit cubes in a 3D diagram to determine volume in cm³
- Measure the volume of a small container by filling it with centimetre cubes
- Express a measured volume using the correct cubic unit notation
The lesson
A unit cube is a cube that is exactly 1 unit long, 1 unit wide, and 1 unit tall. If the unit is a centimetre, its volume is 1 cubic centimetre, written 1 cm³. To find the volume of a bigger shape, count how many unit cubes it takes to build it completely.
Ali stacks centimetre cubes into a box shape: the bottom layer has 3 rows of 3 cubes, and the top layer matches it. Layer 1 has 9 cubes, layer 2 has 9 more. 9 + 9 = 18. Some cubes are hidden inside the stack, but they still count. The volume is 18 cm³.
Always match the unit to the cubes you counted. If the cubes are 1 inch on each side, write your answer in cubic inches (in³), not cm³.
Volume is the number of unit cubes it takes to fill a shape, hidden ones included, written with the matching cubic unit.
Watch it
Where it sits
Learn first
This opens up
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.